Large study finds Covid vaccines are safe in pregnancy

As the HSE’s latest Covid vaccination campaign kicks off, which includes providing second boosters to pregnant women, a new study has confirmed that mRNA vaccines are safe to take in pregnancy.

Pregnant women are at an increased risk of suffering severe Covid-19 compared to their non-pregnant counterparts and vaccines have been recommended for this cohort since early on in the pandemic.

However, according to the study’s lead author, Dr Manish Sadarangani from the British Columbia Children's Hospital Research Institute in Canada, during the early stages of the Covid-19 vaccine rollout, “there was low vaccine uptake among pregnant people due to concerns about data availability and vaccine safety”.

“There still is lower than average uptake among non-pregnant women of reproductive age,” he noted.

The study involved over 191,000 women aged between 15 and 49 and it is the first to compare vaccine side-effects in three different groups:

-Vaccinated pregnant women

-Unvaccinated pregnant women

-Vaccinated non-pregnant women.

Between December 2020 and November 2021, all vaccinated participants were asked to self-report any health events during the seven days following each dose of the vaccine. The unvaccinated pregnant control group was asked to record any health problems over the seven days before they filled out the survey.

A ‘significant health event’ was defined as a new or worse health event which was enough to cause the participant to miss school/work, require medical consultation and/or prevent daily activities in the previous seven days. A ‘serious health event’ was defined as any event resulting in an emergency department visit and/or hospitalisation in the previous seven days.

The study found that 4% of vaccinated pregnant women reported a significant health event within seven days of their first vaccine dose, while 7% experienced this after dose two.

The most common significant health events after dose two in pregnant females were feeling generally unwell, suffering a headache/migraine or developing a respiratory tract infection.

In comparison, in the vaccinated non-pregnant control group, 6% reported a significant health event in the week after dose one and 11% after dose two. Meanwhile, 3% of pregnant unvaccinated participants reported similar events in the seven days prior to survey completion.

The researchers found that serious health events were rare in all groups (fewer than 1%) and occurred at similar rates in vaccinated pregnant women, vaccinated non-pregnant women and unvaccinated controls after dose one and dose two.

Overall, miscarriage/stillbirth was the most frequently reported adverse pregnancy outcome, however, there was no significant difference between the rates of these in vaccinated and unvaccinated women.

“Large, observational studies like ours are crucial for proper understanding of the rates of adverse health events in pregnant women after different doses of Covid-19 vaccination. This information should be used to inform pregnant women about the side-effects they may experience in the week following vaccination,” Dr Sadarangani commented.

The researchers pointed out that this study focused on health events occurring within the first seven days following vaccination and so cannot conclude anything about longer-term reactions. However, a longer-term follow-up of this cohort is ongoing.

The study is published in the journal, The Lancet Infectious Diseases. Writing in a linked comment, Dr Sascha Ellington and Dr Christine Olson from the Centers for Disease Control and Prevention in the US said that these findings “are consistent with and add to the growing body of evidence that Covid-19 mRNA vaccines are safe during pregnancy”.

“Covid-19 vaccination among pregnant people continues to be lower than among non-pregnant females of reproductive age. Given the risks of significant illness and adverse pregnancy outcomes, it is imperative that we continue to collect and disseminate data on the safety and effectiveness of Covid vaccination in pregnancy and to encourage healthcare providers to promote vaccination during all trimesters of pregnancy,” they added.